When studying fluid mechanics, you will encounter the terms high viscosity and low viscosity. We’ll go into high viscosity vs low viscosity in depth in this post.
The ability of a fluid to flow is its viscosity. The viscosity of a fluid is said to be low if it moves quickly. On the other hand, if a fluid moves slowly, its viscosity is said to be high.
We’ll look at the basic idea of viscosity before diving into high viscosity vs low viscosity in depth.
The science of the viscosity:
Every movement is accompanied by friction. When it comes to fluids, one of the most essential terms you’ll come across is viscosity. The relative motion of the fluid layers is referred to as fluid flow. Friction will form between these layers as they move, preventing the flow. Thus, the internal resistance felt by the fluid while flowing is termed viscosity.
Suppose a fluid is poured into the tube, then it flows slowly near the wall of the tube and quickly near the axis of the tube. Thus, fluid movement creates shearing as the speed of the fluid is different near the wall and near the axis, as shown in the following figure.
Viscosity can be grouped into two categories based on fluid flow resistance:
- High viscosity
- Low viscosity
Let’s talk about high viscosity vs low viscosity, which is the focus of this post.
The difference between high and low viscosity:
The following describes the difference between high and low viscosity:
|High viscosity||Low viscosity|
|When a high internal friction force occurs during the relative motion of adjacent layers, the fluid is said to have a high viscosity.||When a low internal friction force occurs during the relative motion of adjacent layers, the fluid is said to have a low viscosity.|
|Fluids cannot easily shear due to their high resistance.||Fluids can easily shear due to their low resistance.|
|To overcome friction or move through a viscous fluid with a high viscosity, one needs a lot of force.||To overcome friction or move through a fluid with low viscosity, one needs less force.|
|The movement of fluid with high viscosity is sluggish or slow.||The movement of fluid with low viscosity is quick.|
|Examples: Air, water etc.|
Image credits: Pixabay Free image
|Examples: Honey, pitch etc.|
Image credits: Pixabay Free image
Viscosity is the relative property. If you consider air and water, water has a higher viscosity than air as the air feels less resistance while flowing than water. But if you think of water and honey, then water has lower viscosity than honey. That is why water can flow with ease than honey.
Water is used as a viscosity indicator. If a fluid has a viscosity greater than that of water, it is termed viscous; if it has a viscosity less than that of water, it is considered mobile.
Viscosity of some common fluids:
The viscosity of some common fluids is mentioned in the chart below, ranging from low to high.
|Glycerine||1000 – 2000|
|Honey||2000 – 3000|
|Ketchup||5000 – 20000|
|Peanut Butter||104 – 106|
|Pitch||2.3 x 1011|
Fluids with extremely high viscosity, such as peanut butter and pitch, act like solids.
What happens when the viscosity of fluid is too high?
⇒ High viscosity means the fluid feels high resistance between the adjacent layers of the fluid during their relative motion. As high viscous fluids have high internal friction between adjacent layers of fluids, they can not shear easily.
The flow of viscous fluid slows down due to the hard shear. As a result, high force is required to overcome the high friction existing between adjacent layers of fluid. That is why it is easier to sail a boat in water than oil, as oil has high viscosity.
Why is viscosity important in everyday life?
⇒ The importance of viscosity may be shown in the following areas:
- While pouring oil into your vehicle, you need to take care of its viscosity. Viscosity decides the oil consumption in your vehicle. Moreover, the fluid’s viscosity index is low; then, during summer, it becomes thinner. Thus, you need to use fluid with stable viscosity so that it does not react to heat or cold.
- In the Millikan oil drop experiment, to determine the charge of an electron, the concept of viscosity of the fluid is used.
- When blood is flowing via veins and arteries, the viscosity of the blood must be taken into account.
- High viscous liquids are used to dampen the motion of various instruments. Break oil is used in hydraulic brakes and is made out of high viscosity liquids.
- Some viscous fluids, such as honey, are utilized to give texture. When honey is added to a meal, the texture changes, and the “mouth feel” changes.